Why Do Dogs Have Tails?
We all love to see a dog wagging its tail but does it always mean that it is happy? Or does it mean something else? Why do dogs even have tails? There are actually many reasons dogs have tails and their tails have many different uses.
When a dog is running and has to turn quickly, he launches the front part of his body in the direction he wants to go. Sometimes he turns so quickly, that his hind legs continue in the original direction, which could cause the dog to topple over, or at the very least, slow him down. If the dog throws his tail in the direction his body is turning, the tail acts as a counter weight and reduces the tendency to spin off course.
When a dog is walking along a narrow surface, if his body tilts to one side, he will often swing his tail in the other direction to maintain his balance, in a similar way to a tightrope walker using a balance bar.
Dogs who enjoy swimming also use their tail as a rudder to help them change or maintain direction in the water.
It is likely that the initial purpose of a dog’s tail was balance but over generations, the dog has evolved to use its tail to communicate information about how he or she is feeling. Evolution has made tails even more visible, such as tails with a light or dark tip, a lighter underside or a bushy shape.
The height, speed and direction of the tail wag all signifies something about the dog’s mood and intentions. The commonly held belief is that a dog wagging its tail is happy and friendly. While this is sometimes the case, tail wagging can also indicate fear, insecurity, a social challenge or a warning.
If your dog has a very short tail, or its tail has been docked, it will make it harder for you and others to interpret how your dog is feeling. Dogs with very short tails cannot communicate as well as others and such dogs often have difficulties interacting with others.
How To Interpret The Wag Of A Dog’s Tail
The tail’s height is often the first indicator of how the dog is feeling. If the tail is held horizontally, the dog is alert and attentive, but relaxed.
If the tail is held further up, it indicates that the dog is feeling confident and is often a sign that the dog is becoming more threatening. A vertical tail is a strong signal that the dog is issuing a warning to back off.
If the tail is held low, it is a sign that the dog is being submissive, worried or possibly sick. A tail tucked low under the body is a sign of anxiety or fear.
It should be noted that different breeds naturally carry their tails at different heights, so when looking for an indication of the dog’s emotional state, the position of the tail should be read relative to the average position where the individual dog normally holds its tail.
Speed and Movement
Generally, the speed of the tail wag indicates how excited the dog is, and the breadth of each tail sweep indicates if the dog’s emotional state is positive or negative.
Common tail movements:
- A slight wag, with limited movement. This is usually a tentative greeting. If the tail is held particularly low, the dog is showing signs of some insecurity.
- A broad wag. This is a friendly greeting – the traditional “happy dog wag”.
- Small, quick movements. This is usually a sign that the dog is about to do something. If the tail is held high, and moving in this way, it is usually a threat.
Recent research has concluded that the direction a dog wags its tail also tells us something about how they are feeling. If dogs feel generally positive about something or someone, their tails wag more to the right side of their rear ends, and when they are feeling negative, their tail wagging is biased to the left. This is not as surprising as it first appears, as similar behaviour is noted in other animals. The right side of the body is controlled by the left side of the brain and the left side of the brain controls the right side of the body. In many animals, including humans, monkeys and birds, the left side of the brain is associated with positive feelings, calmness and a slow heart rate. The right side of the brain is associated with feelings like fear and depression and a rapid heart rate. It is not surprising then, that if the dog is feeling calm and happy, the left side of its brain will be in control, and its tail will wag to the right! If the dog is feeling nervous and its heart is racing, the likelihood is that the right side of its brain is in control and its tail will wag to the left.
The height, speed, movement and direction of the dog’s tail are all visual communicators, but dogs also communicate by scent. Dogs produce pheromones which are a type of hormone that communicate information between animals. Some important pheromones come from the anal glands which are located under the dog’s tail. Anyone who has been present when their dog’s anal glands have been expressed will know how strong this scent can be! Every time the dog wags its tail the muscles squeeze these glands, releasing some of the dog’s unique scent. The wagging tail then acts as a fan to distribute the scent. A dominant dog with its tail held high is announcing itself confidently. A nervous dog with its tail between its legs is trying to minimise the scent released so as not to draw attention to itself.
Most animals have tails of some description, and they have many uses including displaying, gripping, communication and balance. It is most likely that the original purpose of a dog’s tail was to help them balance, however, our domestic pets have evolved to also use their tails to communicate information to other dogs and other animals. Perhaps communication has become the most important use for a dog’s tail because of their close proximity to humans and the need to communicate with us..?